21 The terms of this utterance of the Lord are disturbing to inattentive hearers and careless, hasty readers. For by saying: He that believes in Me shall not be judged, He exempts believers, and by adding: But he that believes not has been judged already, He excludes unbelievers, from judgment. If, then, He has thus exempted believers and debarred unbelievers, allowing the chance of judgment neither to one class nor the other, how can He be considered consistent when he adds thirdly: And this is the judgment, that the light has come into the world, and men loved the darkness rather than the light? For there can apparently be no place left for judgment, since neither believers nor unbelievers are to be judged. Such no doubt will be the conclusion drawn by inattentive hearers and hasty readers. The utterance, however, has an appropriate meaning and a rational interpretation of its own.
Source: Homilies on the Psalms (New Advent)